1. Field
One or more embodiments of the present invention relate to a method and apparatus for encoding and decoding an audio signal and a speech signal.
2. Description of the Related Art
Conventional codecs are divided into speech codecs and audio codecs. A speech codec encodes or decodes a signal in a frequency band of 50 hertz (Hz)˜7 kilo-hertz (kHz) by using a voice generation model. In general, the speech codec performs encoding and decoding by extracting parameters that represent a speech signal by modeling vocal cords and a vocal tube. An audio codec encodes or decodes a signal in a frequency band of 0 Hz˜24 kHz by applying a psychoacoustic model, as in high efficiency-advanced audio coding (HE-AAC). In general, the audio codec performs encoding and decoding by omitting a signal having low sensibility to human auditory senses.
The speech codec is appropriate for encoding or decoding a speech signal, however, sound quality may be reduced when the speech codec encodes or decodes an audio signal. On the other hand, compression efficiency is excellent when the audio codec encodes or decodes the audio signal, however, the compression efficiency may be reduced when the audio codec encodes or decodes the speech signal. Accordingly, a method and apparatus for encoding or decoding a speech signal, an audio signal, or a combined signal with speech and audio signals, which may improve compression efficiency and sound quality, are required.